Magnetic latch



4 July 22, 1958 P. G..HUGHES 2,844,402

MAGNETIC LATCH Filed Au 22, 1957 FIG.Z

' INVENTOR.

PHILIP G- HUGHES HIS ATTORNEY United States Patent 2,844,402 MAGNETIC LATCH Philip G. Hughes, Anchorage, Ky., assignor to General Electric Company, a corporation of New York Application August 22, 1957, Serial No. 679,585

7 Claims. (Cl. 292-251.5)

My invention relates to magnetic latches and more particularly to magnetic latches for use on appliance and other household cabinets, such as, for example, on clothes dryer cabinets.

It is an object of my invention to provide a new and improved magnetic latch which provides a firm holding action but yet is readily releasable for access to the interior of the cabinet.

Another object of my invention is to provide a magnetic latch in which the door is opened by means of a magnet pole piece with only a small force being required to effect the door opening.

Still another object of my invention is to provide an improved magnetic latch including door opening means which may be easily operated by a foot pedal or the like.

In carrying out my invention in one form thereof, I provide a magnetic latch which includes a magnet and a pair of pole pieces associated with the magnet. The magnet and the pole pieces are mounted on the cabinet with which the latch is to be used, with the pole pieces being disposed on opposite sides of the magnet and with at least one of the pole pieces being pivotally mounted. Suitable armature means are provided on the cabinet door opposite the pole pieces for contacting them as the door is closed, and the magnetic attraction between the pole pieces and the armature means is effective to latch the door in the closed position. For opening the door manually actuated means are provided whereby the aforesaid one pole piece may be pivoted on its mounting, and the pole piece itself is provided with an arm for engaging the door. When the pole piece is pivoted, the contact between it and the armature means is broken attenuating the magnetic latching action, and also the arm is moved against the door to push it open. Thereby through the action of the pole piece the door is opened with only a small force being required from the actuating means.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawing in which:

Fig. 1 is a perspective view of a clothes dryer incorporating a preferred embodiment of my new and improved magnetic latch;

Fig. 2 is a front elevational view of the magnetic latch with its cover plate removed;

Fig. 3 is a vertical sectional view of the latch, with certain surfaces broken away to show details, and with certain parts shown in dotted lines to illustrate the door opening operation; and

Fig. 4 is a fragmentary side View of the foot pedal means used to actuate the latch for opening the door.

Referring now to Fig. 1 I have shown therein a clothes drying machine 1 having a clothes tumbling basket 2 arranged fior rotation about a horizontal axis. The clothes "ice tumbling basket 2 is mounted within an outer enclosing cabinet 3, and a door 4 is provided on the cabinet for access to the interior of the basket. During the operation of the machine 1 warm dry air is blown into the basket 2 through an opening 5 in a rear bulkhead closing the back of the basket. After passing through the basket and extracting moisture from the clothes therein, this air is then discharged into an exhaust opening 6 through a passageway 7 in the door 4. It will be understood that the machine 1 is provided with suitable air moving and heater means for creating this flow of warm dry air.

In order to hold the door 4 closed during the operation of the machine I have provided it with a magnetic latch assembly which embodies my invention in one preferred form thereof. This magnetic latch assembly includes a permanent magnet 8 and two pole pieces 9 and 10 which are associated with the magnet. The magnet may be formed of any suitable permanently magnetizable material as, for example, sintered ferromagnetic ferrite, and the pole pieces may be formed of any high permeability magnetizable material as, for example, mild steel. As is best shown in Fig. 2 both the magnet 8 and the pole pieces 9 and 10 are pivotally mounted on a bracket 11 by means of a pivot pin 12. The bracket 11, as shown, actually comprises two separate dished members 11a and 11b held firmly together by means of rivets 13 at their opposite ends. The pole pieces are disposed on opposite sides of the magnet so that in effect they form a sandwich with it, and the pivot pin 12 extends between the opposite sides 11a and 11b of the bracket 11 through the sandwich. The field direction of the magnet 8 is generally parallel to its front face (as viewed in Fig. 2) and thus when it and the pole pieces are mounted on the bracket 11, the flux lines pass into the pole pieces so that one pole piece becomes a magnetic north pole and the other a mag netic south pole.

The pivotal mounting of the magnet and the pole pieces allows them to pivot around a horizontal axis parallel to the front panel 14 of the cabinet 3. And by this pivoting the pole pieces automatically correct for any misalignment of the door 4 with regard to the panel 14 about that axis. In other words they pivot so as .to engage the door across the entire length of their front faces instead of with just a point contact. In order to correct also for misalignment of the door about a vertical axis parallel to the front panel 14, the supporting bracket 11 is itself mounted for slight movement about that axis. The bracket 11 is provided with tongues 15 and 16 at its opposite ends, and to support the bracket these tongues are fitted into slots 17 and 18 formed in flanges 19 and 20 of the dryer front wall or panel 14. The flanges 19 and 20, as shown, protrude rearwardly from the Wall 14 and the tongues 15 and 16 extend respectively upwardly and downwardly into the slots in the flanges. To allow for slight pivotal movement of the bracket around the vertical axis the slots 17 and 18 are somewhat wider than the width of the tongues 15 and 16 (see Fig. 2), and this extra room in the slots permits the bracket to turn somewhat about the vertical axis so that the front faces of the pole pieces 9 and 10 may align themselves with the dryer door.

Positioned in front of the magnet and the pole pieces is a cover plate 21 which is attached to the dryer front wall 14 by any suitable means, as, for example, by screws. The pole pieces extend through this cover plate through suitable slots provided therein, and when the door is closed, they engage a strike or armature plate 22 which is mounted on the dryer door 4 oppositely of them. This strike or armature plate 22 is formed of any suitable magnetic material, as, for example, mild steel, and when it engages the two pole pieces, the magnetic attraction between the pole pieces and the armature holds the door in the closed position. The pole pieces 9 and 10 may, of

course, pivot around the pin 12 so as to correct for any misalignment of the door about a horizontal axis, and the bracket 11 with the magnet and pole pieces may pivot to correct for any misalignment around a vertical axis. will be understood, of course, that the -inner face-of the door 4, if it is formed of magnetic material, may itself serve as the armature means, but ordinarilyitlhas been found preferable to provide a separate. plate for that purpose. a

By my invention the one pole piece 9 in addition to serving as part of the magnetic means for holding the door closed, also serves as the means whereby the door may be opened for loading and unloading of the machine. For that purpose and as is best shown in Figs. 2 and 3, the pole piece 9 is provided at its lower end with a downwardly and outwardly extending arm 23. This protruding arm 23 is positioned behind an aperture 24 in the cover plate 2% and when the pole piece 9 is pivoted in the counterclockwise direction as viewed in Fig. 3 the arm 23 moves outwardly through the aperture so as to engage the door. Or more exactly, it engages the strike plate 22. To avoid the passage of a substantial amount of. leakage flux through the arm 23 when the door is closed, which would, of course, reduce greatly the mag netic holding action, the outer end of the arm 23 is spaced slightly back of the front face 25 of the pole piece 9 so that a slight gap appears between the end of the arm and the strike plate 22 when the door is in its closed position. This gap presents a very high magnetic reluctance and thereby prevents any substantial flux leakage through the arm 23. The spacing of the end of the arm 23 back of the face 25 may be quite small since only a narrow gap is required; for example, in one embodiment of the illustrated latch a spacing of 0.04 inch has been found to be sufficient.

To open the door the pole piece 9 is pivoted counterclockwise as shown by the arrow in Fig. 3, which pivoting produces two separate actions. The first thing which happens is that the pole face 25 is tilted away from the strike plate 22 so that a much greater reluctance is presented in the magnetic circuit. The magnetic attraction holding the door closed is thus greatly attenuated. Substantially immediately after the pole face 25 tilts away from the strike plate 22 the arm 23 is moved against the strike plate and forces it andthe door outwardly as shown by the dotted lines in Fig. 3. In other words a force is applied to the door through the arm 23 as the pivoting continues, which moves it outwardly against the reduced magnetic latching action. The door is in fact pushed'far enough by the arm that the magnetic latching action is terminated and the door is free to swing fully open. Thus, the door may be opened readily, simply by pivoting the pole piece 9 about the pivot pin 1.2.

In my preferred embodiment the force for opening the door is applied to the pole piece 9 by means of a foot pedal 26. As shown in Figs. 1 and 4 the foot pedal 26 is pivotally mounted on the base 27 of the machine by means of a pair of inwardly extending arms 28. Specifically, the arms 28 are mounted at their inner ends on a pivot pin 29 which is journaled in brackets 3t).on the machine base, and when the foot pedal is depressed, the pedal and the arms pivot downwardly together. Between the foot pedal 26 and its pivot-2.8 a linkage member or rod 31 is attached to one of the foot pedal arms 29. This rod extends upwardly from the foot pedal arm to the pole piece 9 and is attached to a tab 32 formed on the pole piece at its lower left hand end (as viewed in Fig. 3). With this arrangement, when the foot pedal is depressed, the rod 31 is moved downwardly and through its connection with the pole piece 9 causes the pole piece to pivot in the counterclockwise direction. This, of course, breaks the magnetic circuit between the pole piece and the armature means 22 on the door and through the action of the arm 23 forcesthe door open. In other words, thepivoting of pole piece in addition to breaking the magnetic circuit causes the pole piece to act as a bell crank forcing the door open.

In order to return the pole piece 9 to its normal or retracted poistion after the door is opened, a spring 33 is provided at the upper end of the pole piece. This spring is mounted between the front wall 14 of the door and a tab 3-2- provided at the upper end of the pole piece, and it normally biases the pole piece about the pivot pin 12 in the clockwise direction (as viewed in Fin. 3). in particular it biases the pole piece 9 sufliciently that the arm 23 is normally retracted within the cabinet. When the foot pedal as is depressed the pole piece is, of course, moved to the dotted line position shown in Fig. 3, opening the door and stretching the spring 33. And when the pressure is then released from the foot pedal, the spring contracts retracting the arm 23 and the pole piece 9 back within the cabinet.

From the above it will be seen that I have provided a new .and improved magnetic latch which provides a firm holding force but yet is readily releasable for access to the basket. By means of the pivoting pole piece the magnetic circuit is first broken and then the door forced open with only a very slight force required from the foot pedal. The double use of the pole piece not only as a part of the magnetic circuit but also as the door actuator, in addition to its functional advantages, also provides for a relatively inexpensive construction. Further, besides these door opening aspects the latch is also very advantageous in that it provides for correcting misalignment of the door about both vertical and horizontal axes.

While in accordance with the patent statutes I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifiactions may be made therein without departing from the invention and it is therefore aimed in the appended claims to cover all such equivalent modifications as fall within the time, spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A magnetic latch assembly for releasably holding a door member in a closed position against a cabinet member, comprising a magnet and first and second pole pieces associated with said magnet, means mounting said magnet and said pole pieces on one of said members with said pole pieces being disposed on opposite sides of said magnet and with at least said first pole piece being pivotally mounted, armature means onthe other of said members opposite said pole pieces for contacting said pole pieces, whereby said door member is held closed by the attraction between said pole pieces and said armature means, said first pole piece having a protruding arm for engaging said other member, and manually operable means for pivoting said first pole piece to break the contact between said first pole piece and said armature means and to move said arm against said other member, whereby said door member is forced open by the movement of said arm.

2. A magnetic latch assembly for releasably holding a door in a closed position against a cabinet, comprising a magnet and first and second pole pieces associated with said magnet, means mounting said magnet and said pole pieces on said cabinet, with said'pole pieces being disposed on opposite sides of said magnet and with at least said first pole piece being pivotally mounted, armature means on said door opposite said pole pieces for contacting said pole pieces, whereby said door is held closed by the attraction between said pole pieces and said armature means, said .first pole piece having a downwardly and outwardly extending arm for engaging said door, and manually operable means for pivoting said first pole piece to break the contact between said first pole piece and said armature means and to move said arm against said door, whereby said door is forced open by the movement of said'arrn.

3. A magnetic latch assembly for-releasably holding a door in a closed position against a cabinet, comprising a magnet and first and second pole pieces associated with said magnet, means mounting said magnet and said pole pieces on said cabinet, with said pole pieces being disposed on opposite sides of said magnet and with at least said first pole piece being pivotally mounted, armature means on said door opposite said pole pieces for contacting said pole pieces, whereby said door is held closed by the attraction between said pole pieces and said armature means, said first pole piece having a downwardly and outwardly extending arm for engaging said door, a foot pedal, linkage means connecting said foot pedal to said first pole piece for actuating said first pole piece from said foot pedal, said first pole piece being pivoted upon the depressing of said foot pedal to break contact with said armature means and to move said arm against said door, whereby said door is opened, and spring means for returning said pole piece to its normal position upon the release of said foot pedal.

4. A magnetic latch assembly for releasably holding a door in a closed position against a cabinet, comprising a magnet and first and second pole pieces associated with said magnet, means pivotally mounting said magnet and said pole pieces on said cabinet, with said pole pieces being disposed on opposite sides of said magnet, armature means on said door opposite said pole pieces for contacting said pole pieces, whereby said door is held closed by the attraction between said pole pieces and said armature means with said pole pieces pivoting to correct for any misalignment of said door, said first pole piece having a downwardly and outwardly extending arm for engaging said door, and manually operable means for pivoting said first pole piece to break the contact between said first pole piece and said armature means and to move said arm against said door, whereby said door is forced open by the movement of said arm.

5. A magnetic latch assembly for releasably holding a door in a closed position against a cabinet, comprising a magnet and first and second pole pieces associated with said magnet, a bracket mounted on said cabinet for limited movement about a vertical axis, means mounting said magnet and said pole pieces on said bracket for pivotal movement about a horizontal axis, with said pole pieces being disposed on opposite sides of said magnet, arm-ature means on said door opposite said pole pieces for contacting said pole pieces, whereby said door is normally held closed by the attraction between said pole pieces and said armature means with said bracket and said pole pieces pivoting to correct for any misalignment of said door, said first pole piece having a downwardly and outwardly extending arm for engaging said door, and manually operable means for pivoting said first pole piece to break the contact between said first pole piece and said armature means and to move said arm against said door, whereby said door is forced open by the movement of said arm.

6. A magnetic latch assembly for releasably holding a door in a closed position against a cabinet, comprising a magnet and first and second pole pieces associated with said magnet, means mounting said magnet and said pole pieces on said cabinet, with said pole pieces being disposed on opposite sides of said magnet and with at least said first pole piece being pivotally mounted, armature means on said door opposite said pole pieces for contacting said pole pieces, whereby said door is normally held closed .by the attraction between said pole pieces and said armature, said first pole piece having a protruding arm for engaging said door, the outer end of said arm being spaced slightly back from the face of said first pole piece engaging said armature means, thereby to reduce the magnetic flux leakage through said arm when said door is closed, and manually operable means for pivoting said first pole piece to break the contact between said first pole piece and said armature means and to move said arm against said door, whereby said door is forced open by the movement of said arm;

7. A magnetic latch assembly for releasably holding a -door in a closed position against a cabinet, comprising a magnet and first and second pole pieces associated with said magnet, a bracket mounted on said cabinet for lim ited movement about a vertical axis, means mounting said magnet and said pole pieces on said bracket for pivotal movement about a horizontal axis, with said pole pieces being disposed on opposite sides of said magnet, armature means on said door opposite said pole pieces for contacting said pole pieces, whereby said door is normally held closed by the attraction between said pole pieces and said armature means with said bracket and said pole pieces pivoting to correct for any misalignment of said door, the outer end of said arm being spaced slightly back from the face of said first pole piece engaging said armature means, thereby to reduce the magnetic flux leakage through said arm when said door is closed, and foot pedal operated means for pivoting said first pole piece to break the contact between said first pole piece and said armature means and to move said arm against said door, whereby said door is forced open by the movement of said arm.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,144 Taylor et a1. Aug. 12, 1941 2,565,891 Sherman Aug. 28, 1951 2,808,281 Poe Oct. 1, 1957 

